It is not uncommon for patients who have had laser refractive surgery more than a decade ago to come in to one's office looking for solutions to changes in their vision over the past few years.
Some patients presenting for evaluation have had some regression of effect as their eyes have aged, whereas others had their procedure in their 30s and now have presbyopic vision. Most patients are eligible for further refractive surgery to help improve their vision. It is critical to perform a comprehensive evaluation to ensure that patients are appropriate candidates, however, because some patients may have developed cataracts, epithelial basement membrane disease (EBMD), dry eye, or even irregular astigmatism.
The evaluation process is similar to that of a patient who has not had surgery. Corneal topography is critical to ensure that the ablation is centered and the optical zone is of reasonable size. As well, the topography should be evaluated to determine whether any signs of early ectasia are present.
Another consideration is the overall keratometry value. If the central K measurements are very flat or very steep, and surgery is required that will flatten or steepen the cornea further, then the patient may not be the best candidate for a laser vision correction enhancement. Corneal topography also is a useful tool for evaluating the tear film. An unstable tear film will show up on corneal topography as focal areas of irregularity or even areas of image drop-out.
Evaluating the refractive error also is critical. The refraction should be stable before an enhancement is performed. As well, if the patient's vision is not correctable to 20/20, the reason for reduced vision should be explored extensively.
One common cause of a refractive shift and mild loss of best-corrected visual acuity (BCVA) is the development of an early cataract. Other causes of reduced BCVA include EBMD, ocular surface disease, and macular conditions. Of these conditions, ocular surface disease caused either by dry eye or blepharitis is treatable, and some patients who have their ocular surface disease successfully treated may experience improvement in their overall quality of vision and decide that further surgery is unnecessary.